Splitscreen#launchIntent: Allow usage with non-fullscreen displays.

When displays are not in fullscreen, tasks that are in fullscreen are
explicitly set as WINDOWING_MODE_FULLSCREEN as opposed to UNDEFINED that
inherits from parent windowing mode. Because of this, when we try to
then start a splitscreen pair with the existing task, which starts off
with reparenting the task to Main Stage, its windowing mode sticks - it
does not change (stays as FULLSCREEN). Then, Shell Transition framework
sees it as a no-op and does not include the Task as part of the Change
list, and so Splitscreen transition code fails to see a task to animate
and aborts the splitscreen setup.

By resetting the windowing mode and explicitly look for it in the Hop
processing, we can allow the task to be reparented and detected by shell
transition correctly.

This also introduces a new flag to disable a logic in which we restore
the task bounds to mLastNonFullscreenBounds when the task is in
freeform, which on a desktop-first / freeform display this will happen
now as we temporarily switch the task to UNDEFINED before reparenting.
This disables restoring the bounds since we are not using this variable
anymore - most of the bounds logic is all done at the Shell side.

Test: Manual. Open Chrome and attempt to start New Window using the app
handle (so it starts from shell side)
Bug: 372315420
Flag:com.android.window.flags.disable_restore_non_fullscreen_bounds_on_configuration_change

Change-Id: I9c2608888ce2a46f3bf9786ff8a4f713f7b4dd57